The Vatican has appeared to expand the Catholic Church's tolerance of condoms as a means of fighting HIV, backing their use by female prostitutes, days after the Pope said their use by male sex workers was better than spreading the virus.

Pope Benedict XVI was quoted at the weekend saying condom use by male prostitutes could be a good thing, indicating the user's intention to protect others from a deadly infection, apparently condoning the use of contraceptives for the first time. The Vatican yesterday confirmed that the same message applied to women sex workers.

Observers said the pontiff's message that condom use, and its inherent ability to prevent conception, was justifiable on health grounds, represented a seismic shift by the Church. "This is a game-changer," said James Martin, a Jesuit priest and culture editor of the religious magazine America.

When extracts from interviews with the Pope appeared from the new book, Light of the World, by German journalist Peter Seewald, the pontiff's comments about condom use at first appeared to refer to male prostitutes, because the original German text used the masculine gender for the word.

However, the Vatican spokesman, the Rev Federico Lombardi, said yesterday that the remarks referred to female sex workers as well.

"I personally asked the Pope if there was a serious, important problem in the choice of the masculine over the feminine," Mr Lombardi said. "He told me no. The problem is this... It's the first step of taking responsibility, of taking into consideration the risk of the life of another with whom you have a relationship."